This does require a response. I'm assuming there is a court order for the 6/14 parenting schedule? Two thoughts come to my mind.
First, does she have a counselor? That would provide a neutral outsider as daughter's as a neutral but trained resource.
I remember one incident recorded in
Divorce Poison, page 140 near the end of chapter 5. The 5 year old girl was too young to be convinced to take sides but was somehow forced to reject her grandparent. (Needless to say, kids shouldn't be put in the middle.)
A five-year-old girl faced the same dilemma. She figured out a unique solution to the conflict between her wish to be loyal to her mother and her love for her grandmother, whom she knew her mother hated. She told her grandmother "I hate you," and then added that whatever she said was the opposite of the truth. With this clever device, the girl could simultaneously gratify the need to align with her mother and express her love to her grandmother.
In my own history, I separated and then divorced when my son was a preschooler. He consistently said he wanted to live with me and in the early years would typically resist going back to his mother and even sometimes be crying. However, eventually I did go back to seek custody (which I did get) due to ex's continued disparagement. He was 9 years old, just about D's age. I was surprised when I picked him up at an exchange one day and as soon as he got in my car he immediately blurted out that he wanted to keep equal time. Hmm, now where did that come from?
However, reality check, you're not likely to get her mother to agree to counseling. Then, if forced, she'll probably try to control which counselor is chosen.
Without showing your cards too soon, you can research local counselors and select a short vetted list, keeping in mind which ones accept insurance which covers the child. Then at the proper time, perhaps in court, provide the short list and ask mother to choose from that vetted list. Court should like it since the selection process involves both parents.
Second, take it to family court if her mother does not support following the court ordered parenting schedule. (Kids do not decide...) Odds are H's order lists his custody as joint but doesn't detail how disagreements are resolved and so it defaults to mediation or court resolution. (If H doesn't have
Decision Making or
Tie Breaker status, then that is something he can seek to reduce future litigation.)
I recall one time in court I was trying to explain my son's behaviors. The magistrate said something like, "Does your son get to decide whether he will go to school? No!"
The point was that the parents decide, the child obeys the court order as well as reasonable parenting decisions.She's far too young to decline an exchange or "vote with her feet" as sometimes courts allow older teens of driving age to do.
I do have a concern, if the resistance is overnights now, once that becomes a pattern what will be the excuse when it comes time for camping or holidays?